The nitrogenase of Clostridium pasteurianum is being studied at the molecular level to determine how its components function in the catalysis of dinitrogen reduction. Methods for looking at changes in protein structure caused by magnesum adenosine triphosphate binding and hydrolysis are being devised to see if the energy of ATP reflected in a structural change of the Fe component of nitrogenase is responsible for the reduction of the MoFe protein. In addition the roles of Mo and Fe in N2 reduction are being investigated by observing changes in the metals or their valence states during the functioning of nitrogenase under various steady state and non-steady state conditions. The latter is being investigated by two approaches, 1) by monitoring the state of the Mo and Fe by physical techniques such as X-ray absorption and 2) by studying the way in which these metals are incorporated into the nitrogenase components. A Mo "storage" compound, synthesized only under N2-fixing conditions, is being characterized and its role in the transfer of Mo to the MoFe protein is being investigated. The mechanism by which nitrogenase activity and biosynthesis is regulated by the cell is also under investigation.